Search Results - (Author, Cooperation:D. Andrault)
-
1Latest Papers from Table of Contents or Articles in PressD. Andrault ; G. Pesce ; M. A. Bouhifd ; N. Bolfan-Casanova ; J. M. Henot ; M. Mezouar
American Association for the Advancement of Science (AAAS)
Published 2014Staff ViewPublication Date: 2014-05-24Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsPublished by: -
2Latest Papers from Table of Contents or Articles in PressD. Andrault ; S. Petitgirard ; G. Lo Nigro ; J. L. Devidal ; G. Veronesi ; G. Garbarino ; M. Mezouar
Nature Publishing Group (NPG)
Published 2012Staff ViewPublication Date: 2012-07-20Publisher: Nature Publishing Group (NPG)Print ISSN: 0028-0836Electronic ISSN: 1476-4687Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsPublished by: -
3Latest Papers from Table of Contents or Articles in PressClesi, V., Bouhifd, M. A., Bolfan-Casanova, N., Manthilake, G., Schiavi, F., Raepsaet, C., Bureau, H., Khodja, H., Andrault, D.
American Association for the Advancement of Science (AAAS)
Published 2018Staff ViewPublication Date: 2018-03-15Publisher: American Association for the Advancement of Science (AAAS)Electronic ISSN: 2375-2548Topics: Natural Sciences in GeneralPublished by: -
4Articles: DFG German National LicensesFontaine, A. ; Baudelet, F. ; Dartyge, E. ; Dubuisson, J. M. ; Giorgetti, C. ; Pizzini, Stefania ; Andrault, D. ; Farges, F. ; Fiquet, G. ; Itié, J. P. ; Polian, A. ; Miguel, A. San ; Tolentino, H.
[S.l.] : American Institute of Physics (AIP)
Published 1995Staff ViewISSN: 1089-7623Source: AIP Digital ArchiveTopics: PhysicsElectrical Engineering, Measurement and Control TechnologyNotes: Measurement of very small differences of the total cross section is the current demand for the spectrometers dedicated to time-dependent experiments carried out under various time-ramped parameters. The dispersive optics and more precisely the full x-ray-absorption spectrometer is mechanically movement-free during data collection which can last over 12 h at LURE-DCI to be sensitive to relative change of the absorption of the order of 10−5. In this range, artefacts due to the drift of silicon lattice spacing under temperature change of the crystal, and drifts of the detector position because of liquid–nitrogen evaporation contained in the cryostat, are sources of errors which have been identified and cured or ... by-passed. The accuracy in difference measurements is now of the order of 10−5 for a total cross section measured equal to 1. In term of optics stability a difference signal of 10−4 out of 1 can be generated by an absorption edge shift caused by a 0.05 K drift of the temperature of the silicon crystal at 7 keV. These performances are essential for the measurement of XMCD in the hard-x-ray range. Water cooling of the dynamically bent crystal reduces dramatically the change of the Si temperature. Adequate geometry makes the spatial drift of the position of the photodiode array much less concerning. The focusing efficiency is also a key parameter to push high-pressure x-ray-absorption spectroscopy (55 GPa), and high-temperature XAS (2000 K), and the combination (15 GPa, 800 K). Simple devices, taking advantage of the focusing geometry, have been successfully tested these last two years. © 1995 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
5Articles: DFG German National LicensesStaff View
ISSN: 1432-2021Source: Springer Online Journal Archives 1860-2000Topics: Chemistry and PharmacologyGeosciencesPhysicsNotes: Abstract The evolution of the distortion of MgGeO3 enstatite and CaGeO3 wollastonite with increasing pressure, has been investigated using X-ray absorption spectroscopy (XAS) in a diamond anvil cell. At room temperature and low pressure (P〈7 GPa), the compressibility of the GeO4 tetrahedron is higher in MgGeO3 enstatite (K [GeO4]∼135 GPa) than in CaGeO3 wollastonite (K [GeO4]≥ 280 GPa). The compression mechanisms of the two compounds are different: the whole mineral compressibility of Ge-enstatite appears to be very homogeneous, in contrast to that of Ge-wollastonite which exhibits an inhomogeneous tretrahedral compressibility. This result is consistent with the variation of the Debye-Waller factors of the two compounds with increasing pressure. At higher pressures, the coordination of germanium atoms in the two compounds gradually changes from fourfold to sixfold. For CaGeO3 the coordination change starts at 7 GPa and is complete a 12 GPa, whereas it starts at about 8.5 GPa for MgGeO3 and is not complete at 31 GPa. The progressive evolution of the measured Ge-O distances as well as the modification in the X-ray absorption near-edge structure indicate two coexisting different sites rather than a progressive site modification. The transformation is found to be partially reversible in CaGeO3 wollastonite, whereas it is totally reversible in MgGeO3 enstatite.Type of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesStaff View
ISSN: 1432-2021Source: Springer Online Journal Archives 1860-2000Topics: Chemistry and PharmacologyGeosciencesPhysicsNotes: Abstract We have investigated the evolution of the distortion of several oxide perovskites with increasing pressure, using EXAFS in the diamond anvil cell. Cubic perovskite BaZrO3 remains cubic up to 52 GPa. Orthorhombic perovskite CaGeO3 becomes less distorted as pressure increases, becomes tetragonal at about 12 GPa and evolves toward cubic structure, still not obtained at 23 GPa. The distortion of orthorhombic perovskite SrZrO3 first increases with pressure up to 8 GPa, then decreases until the perovskite becomes cubic at 25 GPa. The results are interpreted in terms of a systematics, relating the distortion to the ratio f of the volumes of the AO12 dodecahedron and the BO6 octahedron, and to the compressibilities of the polyhedra. For cubic perovskites, f=5, which may correspond to a situation where the compressibilities of octahedra and dodecahedra are equal. The behavior of SrZrO3 offers a clue to predict the evolution of the distortion of MgSiO3 at lower mantle pressures. It is suggested that the increase in distortion experimentally observed at lower pressures should stop above about 10 GPa, and the distortion decrease until the perovskite undergoes ferroelastic transitions to tetragonal and cubic phases, at pressures possibly below the pressure at the core-mantle boundary.Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesStaff View
ISSN: 1432-2021Source: Springer Online Journal Archives 1860-2000Topics: Chemistry and PharmacologyGeosciencesPhysicsNotes: Abstract The effect of (Mg,Fe) substitution on the compression and pressure-induced amorphization of olivines has been investigated up to more than 50 GPa in a diamond anvil cell through energy-dispersive X-ray diffraction experiments with synchrotron radiation. For the four (Mg1−x , Fe x )2SiO4 olivines studied, the compressibility is the highest along the b axis and the smallest along the a axis. For compositions with x = 0, 0.17, 0.66, and 1, the slope of the volume-pressure curves shows a rapid decrease at pressures of around 42, 34, 20 and 10 GPa, respectively. Assuming K′0 = 4, we obtained at lower pressures with a Birch-Murnaghan equation of state essentially the same room-pressure bulk modulus for all olivines, namely K 0 = 131 ± 6 GPa, in agreement with previous single-crystal compression and ultrasonic measurements. At higher pressures, the compression becomes nearly isotropic and the materials very stiff. These changes could precede partial transformation of olivines to a high-pressure polymorph related to the spinel structure. Only a small fraction of olivines seems to transform actually to this phase, however, because most of the material undergoes instead pressure-induced amorphization which take place at considerably higher pressures for Mg-than for Fe-rich olivines.Type of Medium: Electronic ResourceURL: